QUER was purchased from Biospectrum, QU-CAP and caprilic/capric triglycerides (CAP) were obtained from BASF and dimethyl sulfoxide (DMSO) was obtained from Sigma. LLVY-AMC, MG132, as well as primary proteasomal antibodies against α7 (PW8110; 30 kDa) and β5 (PW8895; 23 kDa) subunits were purchased from BIOMOL. Primary antibodies against GAPDH (sc25778; 37 kDa) and secondary antibodies were purchased from Santa Cruz Biotechnology. Primary antibody against tyrosinase (#MS-800-P0, 70-80 kDa) was obtained from Thermo Scientific.